Infrared or heat-seeking detection systems and radar detection systems are employed, for example, for weapon target and guidance, reconnaissance, and classification purposes. Exhaust from the engine of a ship heats visible surfaces of the ship and creates a plume of hot gas, particularly gas turbine engines which produce substantial volumes of high velocity, hot gas when operating at maximum power output. Gas turbines provide high power output to maximize the speed of a ship with relatively small size and light weight which makes them suitable for various sizes of ships, such as small, fiberglass ships, and a variety of combat missions, such as littoral combat. These heated surfaces and plumes of hot gas create an infrared signature that may be detected and used for actively targeting the ship for offensive tactics and other purposes.
Various systems have been employed to suppress the infrared signature created by the exhaust from a ship. Some methods include aspirating cooling air and spraying water or other liquids into the hot exhaust, hiding hot surfaces, and expelling exhaust gas at or below the surface of the water. For example, a previous system has included round mixers with many stages of thin-film cooling. While effective for cooling the exhaust, this type of system creates a protrusion from a normal or conventional exhaust system, such as a series of ejectors projecting above a conventional shroud. This protrusion is identifiable by a radar detection system as creating a different radar signature than would be detected without the exhaust suppression system. Other systems have been developed to reduce the infrared signature, but these systems often are inefficient, are limited in infrared bandwidth, are sensitive to crosswinds, create excess sound or vibration radiation, alter the radar cross-section of the ship, and burden the ship under increased weight vertical center of gravity (KG), power and fuel consumption, and cost. For example, some systems require air pumps, fans, and other active operations for suppressing the infrared signature created by the exhaust.
A new system for suppressing exhaust is needed to address the problem of infrared detection of the heat signature produced by exhaust, such as the exhaust of a gas turbine engine of a ship, while avoiding the deficiencies of prior systems. This need is stressed by the increasing use of gas turbine engines on a variety of ships, such as naval combat ships.